The subject matter disclosed herein relates to transportation refrigeration systems. More specifically, the subject matter disclosed herein relates to filtering of exhaust gas from transportation refrigeration systems.
Fruits, vegetables and other perishable items, including meat, poultry and fish, fresh or frozen, are commonly transported in the cargo box of a truck or trailer, or in an intermodal container. Accordingly, it is customary to provide a transportation refrigeration system in operative association with the cargo box for cooling the atmosphere within the cargo box. The transport refrigeration system includes a refrigerant vapor compression system, also referred to as a transport refrigeration unit, and an on-board power unit. The refrigerant vapor compression system typically includes a compressor, a condenser, an expansion device and an evaporator serially connected by refrigerant lines in a closed refrigerant circuit in accord with known refrigerant vapor compression cycles. The power unit includes an engine, typically diesel powered.
The diesel engine, however, produces harmful soot particles that are removed from the exhaust stream via a diesel particulate filter (DPF). The filter is periodically regenerated, removing the accumulated soot particles from the filter, either via passive or active means. Passive means using the diesel engine exhaust temperature with a catalyst added to the exhaust stream to raise the exhaust gas temperature to combust the soot particles. Active means using the passive system with the addition of injecting added fuel into the exhaust stream, where the added fuel is oxidized by the catalyst to raise the exhaust gas temperature to combust the soot particles.
Transportation refrigeration systems often operate at low speeds and low loads, which results in exhaust temperature below the catalyst activation temperature, the point at which the catalyst will oxidize hydro carbons. During such conditions, the DPF will not successfully passively or actively regenerate.